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windows-10hostshosts-file

What is the maximum length of a host in C:\Windows\System32\drivers\etc\hosts file in Windows?

I have added the following line in my hosts file: C:\Windows\System32\drivers\etc\hosts
127.0.0.1 firsthostfirsthostfirsthostfirsthostfirsthostfirsthostfirsthost

The above is working fine(length is 63), able to ping and the host is responding. But if I put the hostname as
127.0.0.1 firsthostfirsthostfirsthostfirsthostfirsthostfirsthostfirsthostf

(Here the length is 64.),a message is shown: "Ping request could not find host firsthostfirsthostfirsthostfirsthostfirsthostfirsthostfirsthostf. Please check the name and try again."

Please help me to understand the cause. Any reference link would be appreciated.

Thanks in advance.

Solution

  • RFC 1035 limits the length of a fully-qualified domain name (FQDN) to 255 characters, and each "label" - the portion between dots - to 63 characters.

    Your first example works because it's a 63 character label. Your second example fails because it doesn't comply with the rules set out in RFC 1035.